Histidine-rich glycoprotein (HRGP) is a plasma protein with anti-heparin and anti-fibrinolytic activity that has been associated with thrombophilia in three reported families. Therefore, it may promote hypercoagulability. The following objective have been achieved in the laboratory: purification of HRGP, development of an ELISA for its quantitation, confirmation of its anti-heparin activity. An ongoing project is the elucidation of the structure and the possible functional significance of the carbohydrate of HRGP.